Upgrade to Scala.js 1.13.0.

Code changes are forward ports of the following refactorings:

* Split members of ClassDef by type
  scala-js/scala-js@ec3f406
* Unify TreeHash and Versioned into a single Version
  scala-js/scala-js@9f5071f
* Fix scala-js/scala-js#4769: Give JSPropertyDef a hash
  scala-js/scala-js@c2bf430

Author: sjrd